The present invention relates to an axially split inner ring for a fluid flow machine. In addition, the present invention relates to a guide vane ring as well as an aircraft engine.
In fluid flow machines, particularly in axial gas turbines, stator assemblies (hereinafter the terms stator assembly and guide vane ring are used synonymously) are often connected on the radial inner end to inner rings to stabilize the guide vanes and to mount inlet seals. The inlet seals are intended to at least decrease leakage flows between a rotor and the guide vane ring. For the inner rings, there are various designs. For example, there are multi-part inner rings that can be split radially, axially, as well as circumferentially. Axially split inner ring segments are generally screwed together. For attaching or connecting the inlet seals to the inner ring, there are various designs. For example, the inlet seals may be attached to an additional flange. This additional flange can then be connected to the inner ring or to individual inner ring segments, for example by means of screw connections.
One objective of the present invention is to propose an additional attachment or connection of inlet seals to inner rings.
According to the invention, an axially split inner ring designed for connecting to guide vanes is proposed for a fluid flow machine. The axially split inner ring includes at least a first and a second ring segment. The first ring segment is arranged upstream from the second ring segment. The second ring segment has a first sealing segment. Furthermore, at least one section of the second ring segment is arranged radially inward relative to the first ring segment.
Sealing segments can be designed differently, for example as an inlet seal, labyrinth seal, slide seal, and so on. The sealing segments of the axially split ring according to the invention are arranged in particular on the end face radially inward on the inner ring. Sealing segments can advantageously minimize or at least decrease leakage flows between the guide vanes and a radially inward arranged rotor of the fluid flow machine.
Advantageous developments of the present invention are each the subject matter of dependent claims and embodiments.
Sample embodiments according to the invention may have one or more of the features mentioned hereafter.
Fluid flow machines are in particular axial fluid flow machines, for example axial gas turbines.
Axial direction refers in particular to the main through-flow direction of the fluid flow machine. The radial direction is oriented perpendicular to the axial direction. In particular, the longitudinal axes of rotor blades and guide vanes may be oriented radially.
In certain embodiments according to the invention, the second ring segment is connected to at least a first sealing segment. In addition, sections of the second ring segment and sections of the first sealing segment may extend upstream across the axial width of the first ring segment. The first ring segment may be limited or covered radially inward by sections of the second ring segment. Consequently, sections of the second ring segment on a radially inward side of the first ring segment can extend at least across its axial extension.
The at least two ring segments of the axially split inner ring may be constructed in various ways. For example, bearing journals of the guide vanes may be arranged in a dividing plane of the interconnected ring segments. The guide vanes may be adjustable, i.e., they may be rotatable about their longitudinal axis. By means of rotatable guide vanes, various angles of attack can be advantageously adjusted for the incident flow of the rotor blades, to achieve favorable efficiencies of individual, operating points, for example.
The ring segments may be connected to each other in a form-fitting and/or force-fitting manner. For example, a force fit can be achieved by means of ring segment screw connections distributed over the circumference. For example, the second ring segment can surround the first ring segment, or vice versa, or can fit together in a U-shaped manner or an b-shape manner. The ring segments may be connected to each other in a wholly or partially form-fitting manner.
In certain embodiments according to the invention, the first ring segment and/or the second ring segment are segmented in the circumferential direction (perpendicular to the radial direction, whereby the radial direction is oriented perpendicular to the axial direction of the fluid flow machine). For example, the first ring segment and/or the second ring segment may have in the circumferential direction half-rings, each having a circumferential angle of 180 degrees. The ring segments may also be split multiple times, for example in three segments, each with 120 degrees of circumferential angle, in four segments each with 90 degrees of circumferential angle, and so on. The ring segments may also be subdivided into various circumferential angles.
In some embodiments according to the invention, the second ring segment is connected to a second sealing segment or has a second sealing segment. The second sealing segment is arranged downstream from the first sealing segment and/or downstream from the first ring segment. The second sealing segment is constructed in its function and its structure in a manner particularly corresponding to the first sealing segment, particularly as an inlet seal.
In some embodiments according to the invention, the second sealing segment is arranged on a radius that is larger than the average radius of the radial extension of the first ring segment. The average radius of the radial extension of the first ring segment is the geometric average (or half) radius between the radially external and the radially internal radius of the first ring segment. Consequently, the second ring segment is offset radially in relation to the first ring segment and arranged radially further outward. Such an arrangement advantageously allows cavities of the flow channel to decrease downstream from the inner ring.
A cavity may be described, as the region of the flow channel between a guide baffle (which has the inner ring according to the invention radially inward, on the end face) and a subsequent rotor stage with guide vanes. A smaller cavity may reduce the flow losses in the region of the first and second sealing segments. The efficiency of the fluid flow machine can be increased, at least in a few operating points.
In certain embodiments according to the invention, the inner ring has more than two sealing segments. For example, an additional sealing segment may be arranged directly upstream or downstream of the first and/or the second sealing element. Similarly, an additional sealing segment may be arranged on a wider radius that is smaller or greater than the average radius of the radial extension of the first ring segment.
In particular embodiments according to the invention, the sealing segment is an inlet seal. The inlet seal may be referred to or constructed as an inlet coating, a brush-on seal, a hexagonal-pored seal, a honeycomb seal, metal foam, or an open-pored metal sponge. The hollow spaces of the metal sponge can be filled at least regionally with an additional material, such as a polymer for example. By means of an inlet coating, a low-wear or wear-free brushing of a rotor relative to a guide ring (or generally relative to a static fluid flow machine component) can be achieved. The sealing function is achieved on the rotor-side by means of so-called sealing fins, which for example can form a labyrinth seal when a plurality of sealing fins is arranged one after the other on an inlet seal.
In some embodiments according to the invention, at least one sealing segment is connected in a form-fitting and/or material-fitting manner to the inner ring. The inner ring may be referred to as a carrier of the sealing segment. The sealing segment may be connected to the inner ring in a material-fitting manner, particularly by means of adhering or soldering. The sealing segment can also be connected to the inner ring in a form-fitting manner, for example by means of a spring-groove connection. The inner ring can have a circumferential groove, into which segmented seal carriers are placed or inserted about the circumference.
In certain embodiments according to the invention, at least one sealing segment and/or at least one ring segment are produced by means of a generative production method. A generative production method may be referred to as an additive production method or as a rapid prototyping method. Generative production methods include, for example, stereo-lithography, selective laser melting, selective laser sintering, fused deposition modeling, laminated object modeling, 3D printing, as well as cold-gas injection.
In particular, at least one sealing segment and the second ring segment are produced together by means of a generative production method. In doing so, various materials can be used on the one hand for the ring segment, and on the other for the sealing segment, which is constructed in particular as an inlet seal.
Production of the sealing segment and the ring segment in one production step may advantageously allow one to omit performing an assembly step. In addition, the measurement tolerance of the component can be increased or improved, since the assembly step consisting of possible gluing or soldering (which may cause a thermal warpage for example) is no longer necessary.
Some or all embodiments according to the invention may have one, multiple, or all of the advantages mentioned above and/or below.
By means of the axially split inner ring according to the invention, in which the downstream ring segment has at least one sealing segment, the number of parts of the inner ring may be reduced. By means of the functional connection of the ring segment to the sealing segment, a separate seal carrier segment may be advantageously omitted. The assembly effort is consequently decreased. Elevated production tolerances in an assembly with a separate seal carrier segment according to prior art are advantageously avoided. In this way, the overall production costs can be reduced.
By means of the axially split inner ring according to the invention, the number of possible leakage points in the region of the inner ring and the seal may be reduced compared to a design according to prior art having a separate seal carrier. In this way, the efficiency can be advantageously increased.
By means of the axially split inner ring according to the invention, the number of parts and thus the weight of the fluid flow machine can be advantageously reduced. In this way, additional advantages, for example, lower fuel consumption when used in an aircraft engine, can be achieved.
By means of the functional connection of the second downstream ring segment to the sealing segment of the axially split inner ring according to the invention, the size of the cavity between the inner ring and the rotor segment arranged further downstream can be reduced. In this way, flow losses (leakage flows) can be advantageously decreased.
The present invention is explained generically below by means of the attached drawings, in which identical reference signs describe identical or similar components.